FISH DIVERSITY AND ITS THREATENED STATUS OF THE DHARLA RIVER IN BANGLADESH

Raznolikost riba riječnog ekosustava postala je smanjena zbog različitih nepogoda uzrokovanih čovjekom i prirodom. U ovoj studiji, u razdoblju od siječnja do prosinca 2018. godine istraživan je trenutni status biološke raznolikosti riba u rijeci Dharala koja se nalazi (25,8103 ° S, 89,6487 ° E) u sjevernom dijelu Bangladeša. U ovoj je studiji postojeći status biološke raznolikosti riba u rijeci Dharala procijenjen prema indeksu raznolikosti i statusa ugroženosti (kako globalnog, tako i lokalnog). Podaci za uzimanje uzoraka prikupljeni su s tri mjesta na rijeci pomoću različitih ribolovnih alata i tri odabrane ribarnice smještene u okrugu Kurigram u Bangladešu. Ukupno je identificirano 76 vrsta riba koje pripadaju u 8 redova, 26 porodica i 57 rodova. Porodica Cyprinidae koja je bila najdominantnija, bila je zastupljena s 14 vrsta, zatim Danionidae (13 vrsta), Bagridae (8 vrsta) i nekoliko manjih porodica. Osim autohtonih vrsta, zabilježeno je i devet egzotičnih vrsta riba. Indeksi raznolikosti prema Shannon-Weaveru (H), ujednačenosti Pielous (e) i bogatstva Margalefa (D) kretali su se od 3,00 do 3,71, 0,62 do 0,94 i 3,94 do 7,95. Od 76 autohtonih vrsta, 28 vrsta (37%) identificirano je kao ugroženo u Bangladešu, što uključuje kritično ugrožene (4 vrste), ranjive (9 vrsta) i ugrožene (15 vrsta). Neselektivni ribolov trovanjem i razornim ribolovnim spravama identificirani su kao glavne prijetnje biološkoj raznolikosti riba na rijeci Dharla. Iako rijeka Dharla služi kao značajna potpora ugroženim autohtonim ribama, potrebni su određeni koraci da se zaustavi razarajući ribolov, uspostave trajna utočišta za ribe i odgovarajući nadzor za održavanje održive biološke raznolikosti.Fish diversity of a riverine ecosystem became reduced due to different manmade and natural calamities. This study investigated the present fish biodiversity status of the Dharala River located (25.8103° N, 89.6487° E) in the northern part of Bangladesh from January to December 2018. In this study, the existing fish biodiversity status of the Dharala River was estimated in terms of diversity indices and threatened status (both global and local). Data was collected from the three sampling sites of the river using different fishing gears and three selected fish markets located in the Kurigram district of Bangladesh. A total of 76 fish species were identified belonging to 8 orders, 26 families and 57 genera. The Cyprinidae was the most dominant family represented by 14 species followed by the Danionidae (13 species), Bagridae (8 species) and few minor families. Apart from the indigenous species, nine exotic fish species were also recorded. The Shannon-Weaver diversity (H), Pielous evenness (e) and Margalef richness (D) indices ranged from 3.00 to 3.71, 0.62 to 0.94 and 3.94 to 7.95, respectively. Out of 76 indigenous species, 28 species (37%) were identified as threatened in Bangladesh, which included critically endangered (4), vulnerable (9) and endangered (15) species. Indiscriminate fishing through poisoning and destructive fishing gears were identified as the major threats to fish biodiversity of the Dharla River. Thus, the river serves as considerable support for threatened indigenous fishes. Therefore, necessary steps are needed to stop destructive fishing, establish permanent fish sanctuaries and proper monitoring for maintaining sustainable biodiversity in the Dharla River